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J Toxicol Clin Toxicol. 2002;40(2):137-43.

Formate kinetics in methanol poisoning.

Author information

1
Emergency Medicine and Toxicology, Carolinas Medical Center, Charlotte, North Carolina 28232-2861, USA. rkerns@carolinashealthcare.org

Abstract

OBJECTIVE:

We sought to describe the kinetics, dialysis clearance, and laboratory markers of formate (FA), the toxic metabolite of methanol (meOH).

METHODS:

Data were obtained from a prospective, multicenter study of fomepizole +/- dialysis for methanol poisoning. Inclusion criteria confirmed methanol exposure or suspicion of exposure plus either acidemia or abnormal osmolar gap. Dialysis indications were [meOH] > 50 mg/dL, pH < 7.1, refractory acidosis, or visual toxicity. Serial plasma formate, methanol, pH, and electrolyte measurements were made. Formate was determined by gas chromatography. Endogenous and dialysis elimination half-lives were calculated as t(1/2) = 0.693/Ke, with Ke (elimination constant) derived from the slope of log (FA) vs. time. Half-lives were compared with an unpaired Student's t-test. Dialysis clearance was calculated using the Fick Principle. Pearson correlation analysis compared initial formate with initial pH, serum bicarbonate, and anion gap.

RESULTS:

Eleven patients were treated in the study. Eight had detectable formate with mean [FA] of 15.1 mmol/L (range 0.5-34.8). Endogenous elimination half-life was 205 +/- 90 minutes. Elimination half-life during dialysis (n = 5) was 150 +/- 37 minutes, which was not different (t = 0.22; NS). The overall dialysis formate clearance rate was 223 +/- 25 mL/min. Correlation coefficients were: pH vs. formate r2 = 0.93; bicarbonate vs. formate r2 = 0.81; and anion gap vs. formate r2 = 0.76 (all p < 0.05).

CONCLUSIONS:

Although dialysis clears formate, it did not significantly enhance endogenous elimination in our series of patients. Low pH, low bicarbonate, and elevated anion gap correlate independently with formate presence.

PMID:
12126185
[Indexed for MEDLINE]

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